Method for manufacturing semiconductor optical device

A method for manufacturing a semiconductor optical device comprising:

• forming, in a photolithography process, a first resist pattern of a resist film disposed on a top surface of a laminated semiconductor structure including a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type, in sequence, on a substrate, the first resist pattern having a portion shaped in correspondence to a waveguide ridge;
• removing portions of the second semiconductor layer by dry etching, using the first resist pattern as a mask, to form the waveguide ridge and concave portions adjacent to the waveguide ridge, with portions of the second semiconductor layer remaining as the concave portions;
• forming a first insulating film on the waveguide ridge and on the concave portions, leaving the first resist pattern in place on a top surface of the waveguide ridge;
• forming a second resist pattern covering the first insulating film in the concave portions, and exposing a top surface of the first insulating film on top of the waveguide ridge, the second resist pattern having a top surface closer to the substrate than a top surface of the first resist pattern on the waveguide ridge or level with a top surface of the first resist pattern on the waveguide ridge;
• removing the first insulating film by etching, using the second resist pattern as a mask, to expose a top surface of the first resist pattern on the waveguide ridge;
• removing the first resist pattern on top of the waveguide ridge and the second resist pattern;
• and
• forming an electrode layer on the top surface of the second semiconductor layer in the waveguide ridge.